Field
The present disclosure relates generally to methods for cutting and separating strengthened glass sheets into smaller sheet segments, and more specifically to methods for mechanical cutting and separating strengthened glass substrates without inducing undesired sheet breakage.
Technical Background
Chemically strengthened glass sheet has been used in a wide range of applications including protective cover glasses for consumer electronic devices. The ion-exchange process used for chemical strengthening creates a layer of compressive stress on glass surfaces that provides the desired increase in surface damage resistance, but at the same time results in a tensile stress in the mid-section across the thickness of glass.
To obtain chemically strengthened glass sheet components in accordance with current practice, the components are first cut as sheet segments from non-strengthened (non-ion exchanged) glass sheet into the final shape for the desired component, with finishing of the segment edges and shapes to meet aesthetic and functional objectives. Thereafter the glass components go through the ion-exchange strengthening process by immersing the sheet segments into an ion-exchange bath at an optimum elevated temperature and for a time sufficient to develop an engineered stress profile across glass thickness that provides the required surface strengthening effect. Thereafter the components are removed from the bath and cleaned for further processing.
As the applications for chemically strengthened glass widen to cover emerging technologies, such as devices with integrated touch screens, display manufacturers require the ion-exchanged glass to be supplied in larger sheets of glass, for subsequent cutting into the various sizes and shapes of the final components. To reduce the number of components used to support the functionality of touch screen devices, and to lower manufacturing costs, it is increasingly required that the cutting and separation process steps for medium-to-large-size glass panels be conducted on panels previously subjected to ion-exchange strengthening.
Currently available mechanical methods and processes for cutting glass sheet, including thin drawn glass sheet of the kind used for small and large information display panels, have not yet been successfully adapted to the cutting of ion-exchange-strengthened glass without causing glass cracking, due to the relatively high frangibility of many chemically strengthened glasses. Thus increased attention is presently being focused on specialized processes, such as water-jet cutting and the so-called “wet-etching” processes, to enable the efficient cutting and separation of chemically strengthened glasses. Many of these procedures are time-consuming and expensive, however, so there remains a need for an economical yet effective method for separating relatively frangible chemically strengthened glass sheet into sheet segments of predetermined sizes and shapes.